Vapor-electric device



. v g a INVENTOR Joseph S/epmrz ATTORNEY June 17, 1941. SLEPIAN VAPOR-ELECTRIC DEVICE Filed March 51, 1939 WITNESSES:

Patented June 17, 1941 inghousc- Electric &, Manufacturing Company, East Pittsburgh, 2a., a corporation of Pennsylvania.

ApplicationMarch 31, 1939-, Serial No; 265,159 3 Claims. '(cl. 2507275) My invention relates to a vapor-electric deviceand particularly to an improved make-alive electrode for controlling the operation of ignitrontype valves.

Since the discovery of the make-alive principle by Messrs. Slepian and Ludwig, there has been a great deal of research and development work ing toward the development of new make alive materials or constructions, whereby the ene-rgy necessary for starting the cathode spot may be; reduced in order that less expensive control equipment maybe utilized. Most of the materials which have been found commercially satisfactory as make-alive electrodes are very hard crystalline materials, so that they are worked upon; only under difliculties. It has been found that starting electrodes having a roughened surface, as a rule, have a lower starting characteristic than electrodes having smooth surfaces. Also it has been found that by sharpening or tapering the point of the starting electrode where it is immersed in the cathode liquid, the starting ourrent can be reduced approximately 30%, but at an increase in potential of between and I have discovered that, by providing a makealive electrode with a plurality of relatively narrow slots of such width that the surface tension in the mercury will prevent the mercury from flowing into the slots, the starting current can be reduced approximately 50% further with an increase of only 4% to 5% in the necessary starting potential.

Accordingly, it is an object of my invention to provide a make-alive electrode having a plurality of relatively narrow slots therein.

A further object of my invention is to provide a make-alive electrode having a low current starting characteristic.

It is a further object of my invention to provide a make-alive electrode which is extremely strong and resistant to the mechanical impacts caused by movement of the cathode material.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing, in which:

Figure 1 is a sectional elevation of a vaporelectric valve embodying my invention;

Fig. 2 is an enlarged cross-section taken on the line II-II of Fig. 1 and showing the relative proportions of the slots in the make-alive electrode;

Fig. 3 is a detailed figure showing a preferred form of slotting;

, from a lead-in arm 6 mounted through the side; The make-alive electrode I Fig. 4 is a similar view showing another formof slotting, and

Fig. 5 is a fragmentary non-sectional view of probable the bottom portion of the container I and a cooperating main anode l placed abovethe cathode 3. The make-alive electrode 5 is supported of the container I. 7 consistsbf'a body of high resistant material, such silicon carbide, boron carbide, or the com-- merci'al materials's'old underthe trade names of Carbdrundum, Globar an'd Silit". Each of these materials when having the necessary resistivity for successful operation as make-alive electrodes are extremely hard, and consequently hard to machine or otherwise shape.

For successful operation in the make-alive electrode, it is necessary that the electrode 6 shall be in permanent contact with the cathode material 3, while otherwise it is desired to maintain the contact area as small as possible. This has heretofore been accomplished by immersing the tapered tip I of the starting electrode 5 into the mercury 3 approximately one-quarter of an inch, so that any variation in the mercury level will still maintain contact with the make-alive electrode. As to the point of reduced voltage required, it is desirable that the electrode be as short as possible. However, during the operation of the converters, the mercury surface may be quite strongly agitated, so that it is found desirable to maintain the-make-alive connections approximately one-half inch above the cathode surface. Consequently, a practical electrode is approximately three-fourths of an inch in length plus any necessary connections to the lead-in arms. However, it is obvious that if the mercury level is controlled in some manner and the agitation of the mercury surface prevented, much shorter electrodes could be utilized.

I have found that by providing a plurality of relatively narrow slots 8 in the surface of the make-alive electrode 5 exposed to the mercury 3 the necessary starting current is greatly reduced without materially increasing the applied voltage. For example, providing a plurality of slots having a width of approximately .020 of an inch, in some cases gave a reduction of approximately in prevents entrance of mercury into the slots, ma-

terially reduces the power required for successful operation of the make-alive electrodes.

For normal immersion of the electrodes the surface tension of mercury will bridge slots of the order of one millimeter in width but normally narrow slots will be utilized to offset any irregularity in manufacture. The relation between starter slot width and the surface tension of the mercury is graphically illustrated in Fig. 2, which is an enlarged cross section through a slotted electrode in mercury. V

In the fragmentary view of Fig. 5 is illustrated the current concentration now believed to be the reason for the improved starting characteristics. Because of the lack of contact with the mercury in the slots, the current as indicated by the arrows IB crowds into the area adjacent the edge of the slots 8 thus producing a high current gradient at this point.

In Fig. 3 I have demonstrated a preferred method of providing the slots. While apparently it makes little difference whether the slots are,

laterally or longitudinally disposed, I have found that-by providing slightly slanting longitudinally disposed slots 8 the slots 8 may be cut by means of a jeWelers hacksaw, so that they are relatively easy to produce in the hard make-alive material. I

In Fig. 4 I have illustrated another form of slot 8 which may be cut on a suitable milling or grinding machine.

While for purposes of illustration I have shown and described specific embodiments of my invention, it will be apparent that changes and modifications can be made therein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. In a vapor-electric valve having a mercury cathode, a make-alive electrode comprising a body of make-alive material including a base portion and a tapered tip portion, said tip portion extending into said mercury cathode during normal operation of said valve, at least that portion of the tip which extends into the cathode being provided with slots having a width of the order of one millimeter.

2. In a vapor-electric device having a vaporizablecathode and a main anode, a control electrode including a substantially conical tip portion extending into permanent contact with the vaporizable cathode, said conical tip being provided with grooves, said grooves being narrow in width whereby the surface tension of the cathode mate rial prevents the cathode material from entering said grooves.

3. A make-alive electrode for a vapor-electric device having a mercury cathode, comprising a block of high resistance material having a substantially cylindrical top portion and a tapered tip portion, said tapered tip extending into permanent contact with said mercury cathode, that portion of the electrode extending into the mercury being provided with slots having a width of the order of one millimeter.

JOSEPH SLEPIAN. 

